$ { {5} \times \left[\begin{array}{rr}{1} & {2} \\ {4} & {3}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{5}\times{1} & {5}\times{2} \\ {5}\times{4} & {5}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{5} & {10} \\ {20} & {15}\end{array}\right]}$